Polar functional group analysis of mixtures by silicon-29 nuclear magnetic resonance

Abstract

The reaction of primary and secondary amines with 2-dodecen-l-ylsuccinic anhydride provides a simple high-yield route to derivatives that provide useful negative ion SIMS spectra from glycerol solution. Imidization of the amic acid derivative of primary amines provides a method for distinguishing primary and secondary amines. Detection limits for the amic acids lie in the ÍCT® M range and are improved by the use of cationic surfactants such as hexadecylpyridinium acetate. Addition of a cationic surfactant has the additional advantage that glycerol matrix ions are eliminated from the mass spectrum. ACKNOWLEDGMENTWe thank E. A. Williams for assistance with 13C nuclear magnetic resonance spectroscopy.

Qualitative and Quantitative Functional Determination in Bitumen Acidic Fractions by 29Si NMR Spectroscopy. Correlation with Bitumen Aging

“…31 Many authors reported the use of trimethylsilylated compounds and their examination either by 1 H-NMR 25 or by 29 Si-NMR spectroscopy. [32][33][34] Proton NMR spectroscopy gives good quality spectra within a short period of time, but the reduced chemical shift range of trimethylsilyl groups (less than 0.5 ppm) does not permit an unambiguous assignment. A better choice with respect to qualitative and quantitative studies is 29 Si NMR.…”

Silicon-29 NMR Spectral Studies of Kraft Lignin and Related Model Compounds

“…In the previous^tudy (Brezny etaL 1985), we showed that also Si-29 NMR spectra of trimethylsilylated lignins can be routinely obtained at reasonable costs of measuring time and sample amount. Theoretically, under the applied measuring conditions, the proportionality between the Si-NMR signal intensity and the molar concentration of the corresponding trimethylsilyl group lies within 20% for so far known trimethylsilyl derivatives (Schraml 1986). Though this type of Spectroscopy cannot compete in broadness of r nge of chemical shifts with the C-13 NMR Spectroscopy, it possesses some advantages: 1.…”

Molecular Tagging for the Molecular Characterization of Natural Organic Matter

“…Very similar both in structure and silylating potential to BSTFA, this reagent was used to silylate various complex mixtures, including coal, in order to develop 29 Si NMR techniques for enhanced signal in such samples. 74 Monsef-Mirzai et al (1995) used a variety of silylation agents including HMDS and TMCS but also BSA, N-(trimethylsilyl)imidazole (TMSI), and 1-(trimethylsilyl)pyrrolidine (TMSPY) to silylate a number of coal samples. All reactions were carried out under microwave irradiation to achieve complete conversion of all OH groups.…”